<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>novalidate属性</title>
</head>
<body>
    <form id="form" novalidate>
        <fieldset>
            <legend>novalidate属性：</legend>
            用户名：<input type="text" required="true">
            <input type="submit" value="提交">
        </fieldset>
    </form>
</body>
</html>